HDR can be used to produce everything from absolutely incredible to absolutely what the hell is that. We are talking here about the absolutely incredible. The realistic 3D clarity of color and detail to produce a room which looks exactly how it would look if the viewer were actually in the room. You can do that with HDR. Even more so than with a single shot.

I think HDR will help in interior shots. I think it would work well with #4. I understand spotlight is on the dining room but details might appear outside the window on the right and the cupboards on the left.

You are right about taking earlier in the day. This was an improptu shoot as I had the camera in the car when I visited around 1:30, but being a model home they probably won't have it unlocked prior to their opening at 10.

Will experiment with HDR as had heard could be beneficial. Need to build my skill level up and atleast with a D90 can do it vs the prior D40 which theoretically could do it, but a royal pain to go in through the menus to make the bracket adjustments. While those were shot in RAW, assume for HDR would be .jpg output. RAW would seem somewhat self defeating as could go in and change the brackets on the single file. Will experiment with my house and other 'traditional' landscape subjects to gain proficiency.

This isn't my area of photography, but I think you did really well. I might take along a fast lens that's a bit longer than the Sigma in addition to the extreme wide angle. While the Sigma is a pentilinear lens, there's still distortion that you'll have to correct in pp (I know, I have a 12-24). Having a lens along that's more of a normal lens might be quite useful sometimes. It'll never take the place of the Sigma though.

I wouldn't use a fisheye at all. I love my fisheye and use it with interiors for certain effects, but it wouldn't do at all for selling houses.

OK, you can quit laughing now.

As Bynx pointed out, HDR can be used for interiors where you aren't even aware that it was used - it looks just like how your mind would interpret the scene. I'm sure that there will be houses that you'll want to show the view and the interior, and you'd only be able to do that with HDR. I've done it successfully a number of times, but often it doesn't quite work right. It's always worth a try though.

I'm not sure abouy how far you can push it before you'd be open to accusations of mis-selling but a soft HDR approach would work well although it could give the impression that the rooms are lighter than they really are. I did a couple of pseudo-HDR on the default settings with my program and they came out OK so you could try this if you don't want to go back and re-shoot specifically for HDR. It really picks out the texture/patterns on the floor and work surfaces.